Musannaf Ibn Abi Shayba 3:2570

Abu Nu'aym narrated to us, he said: Nusayr ibn Abi al-Ash'ath narrated to us, from Hammad ibn Khawar, from 'Abd al-Malik ibn Maysarah, from al-Nazzal ibn Sabrah, from 'Ali, who said: "When they are three, one of them should go ahead."